A significant portion of water mains throughout North America are made from unlined cast-iron pipe as this was the preferred material for water distribution systems up until the mid-1970s. Over time the carrying capacity of these water mains may be severely reduced or compromised as the pipes begin to deteriorate. One major cause of deterioration in these pipes or conduits is corrosion. As the cast-iron corrodes, the interior wall of the pipe becomes pitted as material is lost, thereby forming tubercules. This corroded material, in combination with mineral deposits, is known as encrustation and tuberculation.
Different solutions exist for addressing these problems. One solution, known as “open-cut replacement”, requires a work area to be excavated to expose the pipe in need of repair and replacing the iron piping system altogether. While this solution may be appropriate where the structurally integrity of the pipe has been too badly compromised to be rehabilitated, it tends to be very costly and labour-intensive and as a result, may not be ideally suited to cases where the structural integrity of the existing pipe remains adequate.
Other solutions involve rehabilitating the pipe or conduit by lining its interior surface with cement mortar (often referred to as a “spray-on liner”) or by deploying a structural liner within the pipe. These conduit rehabilitation solutions may be implemented cost-effectively using trenchless technology techniques which minimize the excavation work required.
Canadian Patent No. 2,361,960 of Mercier describes a method of rehabilitating a conduit having protruding service connections using a cured-in-place structural liner. The liner is made up of two (2) concentric tubular jackets—an outer jacket and an inner jacket—made of a flexible material that is capable of being impregnated by an adhesive resin. Bonded to an inner surface of the inner jacket is an impermeable film made of a material impermeable to liquid. The conduit rehabilitation method described in this patent requires as a preliminary step that the tubular jackets of the liner be impregnated with a curable adhesive resin. The liner is then inserted into one end of the conduit and pulled into place. Once the liner is in position, a shaping step is performed to urge the liner to conform to the inner wall of the conduit. During the shaping or forming of the liner, the liner is pushed up against the protruding end of the service connection. The adhesive resin impregnated within the liner is urged to flow around the threading of the protruding end so as to at least partially fill the spaces defined between the threading of the protruding end. Next heated water is flowed through the now lined conduit to cause the curable adhesive resin to cure. Once cured, the liner will be form a rigid structure that is bonded to the outer surface of the conduit. Thereafter, access to the service connection can be restored by drilling a hole into the liner at the location of corporation stop.
In the field, the method for water conduit rehabilitation described in Canadian Patent No. 2,361,960 has been found to be successful and relatively easy and cost effective to deploy. However, while in most cases, the seal achieved by the cured adhesive resin about the protruding end of the service connection has proven to be adequate, there have been some field applications where this seal has failed. In such applications, the failure of the seal has resulted in water infiltrating or seeping around the corporation stop and between the liner and the outer surface of the conduit, thereby compromising the water tightness of the liner in that region and making remedial action necessary. As it may be appreciated, such remedial action is to be avoided as much as possible as it tends to create a service disruption and tends to increase the costs of conduit rehabilitation.
In light of the foregoing, it would be advantageous to have a method for rehabilitating conduits using cured-in-place structural liners with improved sealing around the service connections so as to obviate the drawbacks associated with the above-described prior art conduit rehabilitation methods. Preferably, such improved sealing could be provided in a relatively simple, cost-effective manner and without unduly extending the time required to carry out the conduit rehabilitation method.